The present invention relates to a synthetic resin-made intake manifold and a manufacturing method thereof, wherein the intake manifold includes a volumetric air-intake section communicating with a intake air supply source through an inlet pipe, and a plurality of outlet pipes for connecting the volumetric air-intake section to cylinders of an internal combustion engine, at least the volumetric air-intake section and each of the outlet pipes being made of a synthetic resin.
As is widely known, an intake manifold is connected to a cylinder head of an internal combustion engine for feeding intake air into combustion chambers of individual cylinders. As such intake manifold, there is known one that includes a volumetric air-intake section (so-called surge tank) communicating with an intake air supply source through an inlet pipe and a plurality (equal to the number of cylinders) of outlet pipes for connecting the surge tank to each cylinder of the engine. Since such intake manifold is a considerably large-size component of an air-intake system, so for purpose of reducing the weight of the peripheral arrangement of the engine more than ever, it has been contemplated that the intake manifold may be formed of synthetic resin instead of conventionally used light alloy (e.g., aluminum alloy and the like).
Since the intake manifold is an air-intake system component which involves lower temperature conditions than air-exhaust system components, it is well possible to use synthetic resin (in particular, a synthetic resin of the type which is reinforced with fibers or the like) as the material.
In the prior art, when fabricating such an intake manifold from synthetic resin, conceivably, one method which would be commonly considered may be such that a pair of synthetic resin-made separate halves integrally formed of a half for a surge tank and a half for outlet pipes, previously formed from synthetic resin are brought into abutment against each other, being then joined together by applying an adhesive to their abutting surfaces or by melting thermally or by applying vibration on the abutted portion, whereby the separate halves are joined together into a finished component (intake manifold).
In manufacturing intake manifolds for mass-production automotive engines, a need exists for a manufacturing method which can assure higher production efficiency. However, in the above mentioned prior art, since forming operation for respective halves takes a lot of time, it is generally difficult to achieve further enhancement of productivity.
Another problem is that since each separate half is integrally formed of a half for a surge tank and a half for outlet pipes, even where the surge tank only or the outlet pipes only is to be design changed, the integration makes it necessary to reconstruct the molding die in its entirety, which is a large limiting factor against the task of enhancing the flexibility of designing. Therefore, for common use of a particular component, for example, surge tank, with the outlet pipe only changed, thereby to promote common utilization of the component with other types of vehicles, considerable expenditure is required with respect to the molding die.
In the recent trend toward saving space of the engine room, with respect to the intake manifold and the mounting arrangement therefor, it is required to make them more compact in size, with setting the length of the outlet pipe be a length not lower than a specified length, or the length of each outlet pipe be as much equalized length as possible, for obtaining satisfactory air-intake characteristic. To this end, it is required that good contrivance be used with respect to the outlet pipe such that the outlet pipe is made more complex in configuration, including not only a simple bending from a comparatively linear straight pipe at a specified curvature, but also a three dimensional bending consists of aforesaid simple bending with twisting applied thereto. Further, along with the size reduction of the surge tank, it is required that joint portions between a plurality of outlet pipes and the surge tank be intensively gathered in as much narrower space as possible, and in view of this fact it is inevitable that the bending configuration of the outlet pipe becomes to a complex one.
However, in above mentioned conventional method, wherein a pair of separate halves integrally formed of a half for a surge tank and a half for outlet pipes, are brought into abutment against each other and jointed together, it is virtually very difficult to meet the size reduction requirement when the outlet pipe is of such a complex shape as above mentioned. Even if the method could be applied, there is a problem that it is difficult to maintain atably high production efficiency and quality.
As a method for molding a synthetic resin-made hollow item, it is known to bring synthetic resin-made halves into abutment against each other and fill a melted resin mass into an internal passage formed along a peripheral edge of the abutted portion or a passage formed between the abutted portion and molding die wall, to thereby join the halves together to obtain a hollow molded product. Also, there is known a method in which filling molten synthetic resin into the passage is carried out, within a molding die in which separate halves are molded when they are joined together in such a way as aforesaid.
By employing such a method it is possible to ensure more stably high strength of bond between the so jointed halves and good sealing performance of the abutted portion as compared with the prior art practice in which such joining is carried out by adhesion or thermal melting.
For example, in Japanese Patent Publication No. 2-38377 there is disclosed a molding die construction including one pair of metal dies which is basically such that one of the metal dies has a male molding portion and a female molding portion for molding one set of separate halves, whereas the other metal die has a female molding portion and a male molding portion provided in opposed relation to the molding portions of the one metal die. In this conjunction, a method using such a pair of molding die (so-called die slide injection (DSI) method) is also disclosed such that after separate halves are simultaneously molded (injection molded), one of the metal die is caused to slide relative to the other metal die so that separate halves remaining in respective female molding portions are brought into abutment with each other, with melted resin being injected onto the peripheral edge of the abutted portion to join the two halves together.
According to this DSI method, productivity can be considerably enhanced as compared with conventional method in which molding of separate halves and abutting/jointing of the halves are carried out at separate stages.
For further improvement of production efficiency, in Japanese Patent Publication No. 7-4830, for example, there is disclosed a rotary injection molding die construction including a combination of molding dies which is basically such that the molding dies are adapted to be opened and closed in relation to each other in such a way that one of the molding dies is rotatable over a predetermined angle relative to the other, each molding die having a molding portion to constitute a rotary injection molding die construction, each die consisting of at least one male molding portion and two female molding portions arranged in a repetitive sequence of male/female/female in the direction of rotation for each rotational run over the predetermined angle. In this conjunction, there is also disclosed a rotary injection molding method (so-called die rotary injection (DRI) method) wherein by using such a molding die assembly, it is possible to carry out molding of separate halves and joining of a pair of abutted halves during each rotational movement (for example, forward/reverse movement), thereby to obtain a finished product for each rotational movement.
Thus, by using the DRI method or DSI method it is possible to obtain high productivity and good quality in a stable condition; however, where separate halves are integrally formed of a half for a surge tank and a half for outlet pipes in applying such a method, as in the case of the prior art, the molding die is of a very large in size, and this causes a problem of lack of practical usefulness.
The present invention has been developed in view of above mentioned problems and, therefore, it is a primary object of the invention to provide a synthetic resin-made intake manifold adapted for efficient production and flexible designing or including outlet pipes having a complex shape, by applying the DRI method or DSI method, and to provide a manufacturing method of the aforesaid synthetic resin-made intake manifold.
Therefore, according to a first aspect of the present invention, there is provided a method for manufacturing a synthetic resin-made intake manifold including a volumetric air-intake section communicating with an intake air supply source through an inlet pipe, and a plurality of outlet pipes connected at one end to cylinders of an internal combustion engine through a mounting member and at the other end to the volumetric air-intake section, the volumetric air-intake section and the outlet pipes being formed of a synthetic resin, wherein the volumetric air-intake section and the outlet pipes are respectively injection molded by the die rotary injection method or die slide injection method and are then assembled together and jointed into unity.
In the synthetic resin intake manifold manufacturing method of the first aspect of the present invention, the volumetric air-intake section and the outlet pipes are separately injection molded by a so-called die rotary injection (DRI) method or die slide injection (DSI) method, and then the former and the latter are assembled and joined together into unity. Therefore, the DRI method or DSI method can be comparatively easily employed in manufacturing the volumetric air-intake section and individual outlet pipes which are to be made of synthetic resin without involving any difficulty (that is, without involving any impractical size increase with respect to the molding die). This makes it possible to steadily obtain higher productivity and higher quality as compared with the prior art.
Further, since the volumetric air-intake section and outlet pipes are separately molded, where only volumetric air-intake section or outlet pipes are to be changed in design, it is only necessary to change separate molding dies, and this provides for design flexibility with respect to intake manifold. Therefore, for common use of a particular component, for example, volumetric air-intake section, with outlet pipes only changed, thereby to promote common utilization of the component with other types of vehicles, it can be comparatively easily achieved with a smaller cost of molding die. Furthermore, the present invention is adapted for ready application even where outlet pipes are bent pipes of a complex shape.
Also, according to a second aspect of the invention based on the first aspect of the invention, the mounting member is integrally formed with the volumetric air-intake section during the process of injection molding of the volumetric air-intake section.
In the synthetic resin-made intake manifold manufacturing method of the second aspect of the invention, basically it is possible to achieve the same effect as obtained in the first aspect of the invention. In particular, since a mounting member for connecting one end of each outlet pipe is integrally molded with the volumetric air-intake section during the process of injection molding of the volumetric air-intake section, the number of components can be reduced and productivity can be further improved.
Further, according to a third aspect of the invention, there is provided a synthetic resin-made intake manifold including a volumetric air-intake section communicating with an intake air supply source through an inlet pipe, and a plurality of outlet pipes connected at one end to cylinders of an internal combustion engine through a mounting member and at the other end to the volumetric air-intake section, the volumetric air-intake section and the outlet pipes being formed of a synthetic resin, the manifold, wherein the volumetric air-intake section and the outlet pipes are respectively injection molded by the die rotary injection method or die slide injection method and are then assembled together and jointed into unity.
In the synthetic resin-made intake manifold of the third aspect of the invention, since the volumetric air-intake section and the outlet pipes which are injection molded by a so-called die rotary injection (DRI) method or a die slide injection (DSI) method are assembled and joined together into unity, the DRI method or DSI method can be comparatively easily employed in manufacturing the volumetric air-intake section and individual outlet pipes which are to be made of synthetic resin without involving any difficulty (that is, without involving any impractical size increase with respect to the molding die). This makes it possible to steadily obtain higher productivity and higher quality as compared with the prior art.
Further, since the volumetric air-intake section and outlet pipes are separately molded, where only volumetric air-intake section or outlet pipes are to be changed in design, it is only necessary to change separate molding dies, and this provides for design flexibility with respect to intake manifold. Therefore, for common use of a particular component, for example, volumetric air-intake section, with outlet pipes only changed, thereby to promote common utilization of the component with other types of vehicles, it can be comparatively easily achieved with a smaller cost of molding die. Furthermore, the present invention is adapted for ready application even where outlet pipes are bent pipes of a complex shape.
Furthermore, according to a fourth aspect of the invention based on the third aspect of the invention, the mounting member is integrally formed with the volumetric air-intake section.
In the synthetic resin-made intake manifold of the fourth aspect of the invention, basically it is possible to achieve the same effect as obtained in the third aspect of the invention. In particular, since a mounting member for connecting one end of each outlet pipe is integrally molded with the volumetric air-intake section during the process of injection molding of the volumetric air-intake section, the number of components can be reduced and productivity can be further improved.
Furthermore, according to a fifth aspect of the invention based on the third or fourth aspect of the invention, each of the outlet pipes is formed of a bent pipe and opposite ends of its axis form an angle of about 180 degree or more in a bending direction of the outlet pipe.
In the synthetic resin-made manifold of the fifth aspect of the invention, basically it is possible to achieve same effect as obtained in the third or fourth aspect of the invention. In particular, since each of the outlet pipes is formed of a bent pipe and opposite ends of its axis form an angle of about 180 degree or more in a bending direction of the outlet pipe, it is possible to make the construction of the intake manifold and the mounting structure more compact, with setting the length of each outlet pipe to be a length not lower than a certain level, or with setting the lengths of outlet pipes to be as much equalized as possible in length in order to provide good air-intake characteristic.